1. Field of the Invention
This invention relates to printing apparatus comprising a printing section including a plurality of drive coils for driving printing hammers arranged longitudinally in side-by-side relation, and more particularly it is concerned with cooling of the drive coils of the printing section.
2. Description of the Prior Art
Printing apparatus of the type described generally comprise a core including a permanent magnet, drive coils located at one side of the core, and printing hammers each having an armature pivoted at one end, part of which constitutes a magnetic circuit. Each of the printing hammers is attracted by the permanent magnet and moves toward the core when no input is applied to the associated drive coil, and when an input is applied to any one of the drive coils, a magnetic field is generated in the magnetic circuit which tends to overcome the magnetic field of the magnetic circuit, to allow the associated printing hammer to be released from engagement with the core. At this time, the printing hammer strikes the paper wound on the platen with a printing pin attached to the printing hammer, to produce characters in the Braille system in patterns composed of raise dots.
The printing hammers are arranged in a plurality of numbers longitudinally of the platen, and the drive coils are equal in number to the printing hammers. The printing section has a longitudinal length of 300 to 600 mm.
In this type of printing apparatus, the drive coils are naturally cooled or forcibly cooled with air. However, as the capacity of the apparatus increases and the printing speed is raised, actuation of the drive coils produces a large amount of heat. Thus, the cooling systems that have been employed in the prior art are unable to meet the requirement of cooling the apparatus of high capacity and high speed operation of the present day.